Copper-zinc alloys comprising manganese silicides are known from the document JP 09316570 A. In these alloys, the proportion of β-phase is up to 30%. The alloys do not contain any phosphorus. The alloys are cast as cylindrical blocks having a diameter of 120 mm. Two hot forming steps at 700° C. and 700-750° C., respectively, are subsequently carried out.
Furthermore, synchronizing rings composed of lead-reduced copper-zinc alloys are known from the document DE 10 2005 059 391 A1. The alloys contain manganese in proportions of from 0.5 to 5% by weight, silicon in proportions of from 0.3 to 2% by weight, aluminum in proportions of from 0.5 to 2.5% by weight, iron in proportions of from 0.3 to 1% by weight and nickel in proportions of from 0.5 to 5% by weight. The phosphorus content is less than 0.02% by weight. Intermetallic phases composed of manganese, iron and silicon are present in the alloys. The copper content varies in the range from 55 to 75% by weight, so that it can be assumed that the phase composition of the respective material is of subordinate importance. The synchronizing rings are produced by cutting machining. The document gives no information about the production of the starting material used there.
In addition, the document DE 10 2007 029 991 B4 discloses copper-zinc alloys which are improved in respect of cold formability and also processes for producing tubes and rods composed of these alloys. In the copper-zinc alloys, the proportions of silicon, manganese, iron and nickel are set so that both iron-nickel-manganese-containing mixed silicides having a stem-like shape and also mixed silicides which are enriched in iron and nickel and have a globular shape are present in the microstructure of the material. The microstructure of the material consists of an α-matrix in which at least 5% by volume and up to 50% by volume of β-phase is embedded in addition to the silicides. The globular silicides are seen as the reason for stabilization of the β-phase taking place. The heterogeneous matrix structure made up of α- and β-phase together with the extraordinarily high content of hard phases, in particular the iron-nickel-manganese-containing mixed silicides, ensures a desirable complex wear resistance of the components composed of these alloys. The processing of the alloy comprises extrusion in a temperature range from 600 to 800° C. This hot forming is promoted by the microstructure having up to 50% by volume of β-phase in the cast state. Tubes composed of these alloys achieve elongation at break values of up to about 13%.
The prior art thus does not disclose any manganese silicide-containing copper-zinc alloys from which materials which have excellent properties for use as sliding elements can be produced by means of processes which comprise only cold forming steps as forming steps.